Optical recorder and laser power control method

ABSTRACT

An optical recording apparatus which obtains the most appropriate recording laser power state in real time according to an environmental mark-generation condidtion. When data is recorded (marks and spaces are generated) by emitting pulse-train-manner laser outputs to an organic-pigment recording medium, a space-period signal value corresponding to a space period is detected in a reflected-light information signal to estimate a first-pulse signal value corresponding to a first pulse. In addition, a second-and-subsequent-pulse signal value corresponding to second and subsequent pulses is detected in the reflected-light information signal. The ratio between the estimated first-pulse signal value and the detected second-and-subsequent-pulse signal value is obtained, and the obtained ratio and a reference ratio are used to generate a laser-power compensation signal to control the power of the laser outputs.

TECHNICAL FIELD

[0001] The present invention relates to optical recording apparatusesfor recording into recording media such as optical disks, andlaser-power control methods.

BACKGROUND ART

[0002] CD-type and DVD-type optical disks have been widely known asoptical recording media. Especially as write-once media and rewritablemedia, media for which data recording can be performed at a user side,and recording apparatuses have also been spread.

[0003] For example, CD-Rs (compact discs recordable) and DVD-Rs (digiralversatile discs recordable) are typically used as write-once media. Inthe disks, organic pigment films are used as disk recording layers, andpits (marks) are formed by organic-pigment changes when a laser isemitted to data tracks formed as pre-grooves.

[0004] When data is recorded in such recording media, if laser power isoptimized, pits are successfully formed and therefore, the quality of areproduced signal is improved when reproduction.

[0005] To this end, when an organic-pigment-film recording medium isloaded into an optical recording apparatus, or immediately beforerecording is started, test writing is executed several times at apredetermined area (test-writing area) of the recording medium whilelaser power is slightly being changed, to determine the recording laserpower which makes the quality of a reproduced signal best in the area.The asymmetry or the jitter of a reproduced RF signal is, for example,used as an evaluation function to evaluate the quality of the reproducedsignal.

[0006] The most appropriate laser power is obtained before a recordingoperation, and so-called APC (automatic laser-power control) is appliedduring recording to output a laser at the most appropriate power.Therefore, a successful recording operation is allowed.

[0007] However, the obtained most appropriate laser power is just forthe test-writing area.

[0008] On the disk, recording-film unevenness may occur from the centerto the peripheral of the disk due to a recording-film forming process inmanufacturing the recording medium.

[0009] Further, the wavelength of a laser output from a semiconductorlaser device generally fluctuates according to the temperature. Thewavelength of the laser emitted to the surface of a recording mediumchanges the optical absorption efficiency of the recording medium. Inother words, even if the laser output power is constant, the energyreceived by the recording film of the disk is changed due to a change inlaser wavelength, and therefore, the state of a pit mark generated bythe energy is also changed. In summary, even if the recording laserpower is output at the most appropriate value, a mark to be generatedmay be shifted from the most appropriate mark state.

[0010] With these points being taken into consideration, the mostappropriate laser power obtained by power calibration performed at thetest-writing area on the disk at a point of time is not necessarily themost appropriate recording laser power for the entire area of the diskor under every environmental condition, which includes temperaturechanges.

[0011] In other words, even when a laser is output by an APC operationat the most appropriate laser power obtained by power calibration, thisdoes not necessarily mean that the most-appropriate recording operation(pit forming operation which causes a high-quality reproduction signalto be obtained during reproduction) is always implemented.

[0012] When an APC operation is performed which employs only the mostappropriate recording power obtained in the testwriting area as a targetvalue, if the quality margin of a reproduced signal is taken intoaccount in a system, it may be effective to suppress the fluctuation ofthe light absorption efficiency of the recording medium as much aspossible, or to employ a laser driving apparatus which has a laser inwhich the fluctuation of the wavelength is unlikely to occur when thetemperature is changed or which has a temperature control mechanism.These measures are, however, technically complicated and disadvantageousin terms of cost.

[0013] The above problem may be avoided by proposing a format in whichthe deterioration of reproduced-signal quality is assumed in advance.This proposal, however, leads in an opposite direction for opticalrecording/reproduction systems for which higher density is stronglydemanded.

DISCLOSURE OF INVENTION

[0014] Under the above situation, an object of the present invention isto allow a recording operation to be always executed at the mostappropriate laser power to obtain a high-quality reproduced signal.

[0015] To this end, an optical recording apparatus according to thepresent invention includes recording processing means for applyingencoding processing to data to be recorded to generate encoded data andfor generating laser driving pulses used for executingpulse-train-manner laser outputs, according to the encoded data;recording-head means for emitting the laser outputs to the recordingmedium according to the laser driving pulses to execute recording of adata string formed of a mark and a space on the recording medium;reflected-light information signal detection means for detecting areflected-light information signal obtained when the recording-headmeans emits the laser outputs; signalvalue detection means for detectinga space-period signal value corresponding to a period of the space and asecond-and-subsequent-pulse signal value corresponding to second andsubsequent pulses in the pulse-train-manner laser outputs, in thereflected-light information signal detected by the reflected-lightinformation signal detection means; estimation means for estimating afirst-pulse signal value corresponding to a first pulse in thepulse-train-manner laser outputs by using the space-period signal valuedetected by the signal-value detection means; calculation means forobtaining the ratio between the second-and-subsequent-pulse signal valuedetected by the signal-value detection means and the first-pulse signalvalue obtained by the estimation means and for generating a laser-powercompensation signal by using the obtained ratio and a reference ratio;and laser-power control means for controlling the power of the laseroutputs according to the laser-power compensation signal sent from thecalculation means.

[0016] In this case, the recording medium has an organic pigment film asa recording layer.

[0017] Further, the signal-value detection means further detects thefirst-pulse signal value corresponding to the first pulse in thepulse-train-manner laser outputs, and the estimation means corrects thefirst-pulse signal value estimated by using the space-period signalvalue, by using the first-pulse signal value detected by thesignal-value detection means.

[0018] The first-pulse signal value is the peak, the center value, orthe modulation value of the reflected-light information signal,corresponding to the first pulse in the pulse-train-manner laseroutputs.

[0019] The second-and-subsequent-pulse signal value is the peak, thecenter value, the bottom value, the average, or the modulation value ofthe reflected-light information signal, corresponding to the whole orpart of the second and subsequent pulses in the pulse-train-manner laseroutputs.

[0020] The calculation means stores in advance the most appropriateratio between the first-pulse signal value and thesecond-and-subsequent-pulse signal value according to each of variousconditions related to a recording operation, and selects a ratio suitedto the current condition among the stored ratios to use it as thereference ratio.

[0021] A laser-power control method according to the present inventionis for an optical recording apparatus which applies pulse-train-mannerlaser outputs to a recording medium having an organic pigment film torecord data. A space-period signal value corresponding to a period ofthe space and a second-and-subsequent-pulse signal value correspondingto second and subsequent pulses in the pulse-train-manner laser outputsare detected in a reflected-light information signal obtained during thelaser outputs; a first-pulse signal value corresponding to a first pulsein the pulse-train-manner laser outputs is estimated by using thedetected space-period signal value; the ratio between the detectedsecond-and-subsequent-pulse signal value and the estimated first-pulsesignal value is obtained; a laser-power compensation signal is generatedby using the obtained ratio and a reference ratio; and the power of thelaser outputs is controlled according to the laser-power compensationsignal.

[0022] Pit marks are formed more quickly with respect to laser emissionon recording media having organic pigment films than on, for example,recording media having general phase-change recording films. In otherwords, an effect of the pit mark being recorded by the current laserillumination appears on reflected light obtained by the laserillumination. “Pit marks are formed more quickly,” described above,means that pit marks are generated so “quickly” that the pit mark beingrecorded changes the quantity of reflected light of the recording laser.

[0023] For such recording media, a mark-generation state can bemonitored in real time by reflected-light information. Therefore,reflected-light information which includes mark-generation informationis observed during recording, it is determined almost at the same timewhether the recording power currently being output is most appropriatefor mark generation, and if the recording power is shifted from the mostappropriate state, a shift compensation is fed back to a laser-powercontrol system to control the laser power so as to be the mostappropriate state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a view showing pulse-train-manner light emission drivingand an RF signal according to an embodiment of the present invention.

[0025]FIG. 2 is a view showing the RF signal.

[0026]FIG. 3 is a view showing an RF-signal waveform obtained when arecording power is changed.

[0027]FIG. 4 is a view showing an RF-signal waveform obtained when therecording power is changed.

[0028]FIG. 5 is a view showing an RF-signal waveform obtained when therecording power is changed.

[0029]FIG. 6 is a view showing an RF-signal waveform obtained when therecording power is changed.

[0030]FIG. 7 is a view showing the relationship between the recordingpower and normalized amplitudes.

[0031]FIG. 8 is a view showing compensation applied to the normalizedamplitudes corresponding to the recording power.

[0032]FIG. 9 is a view showing the relationship between the recordingpower and compensated normalized amplitudes.

[0033]FIG. 10 is a block diagram of a disk drive apparatus according tothe embodiment.

[0034]FIG. 11 is a block diagram of a main part of the disk driveapparatus according to the embodiment.

[0035]FIG. 12 is a view showing RF-signal sampling operations accordingto the embodiment.

[0036]FIG. 13 is a flowchart of recording-power compensation processingaccording to the embodiment.

[0037]FIG. 14 is a flowchart of another recording-power compensationprocessing according to the embodiment.

[0038]FIG. 15 is a view showing the relationship between a ratio andrecording power in the recording-power compensation processing accordingto the embodiment.

[0039]FIG. 16 is a block diagram of another example structure of themain part of the disk drive apparatus according to the embodiment.

[0040]FIG. 17 is a flowchart of another recording-power compensationprocessing according to the embodiment.

[0041]FIG. 18 is a block diagram of another example structure of themain part of the disk drive apparatus according to the embodiment.

[0042]FIG. 19 is a view showing another example of RF-signal samplingoperations according to the embodiment.

[0043]FIG. 20 is a view showing another example of RF-signal samplingoperations according to the embodiment.

[0044]FIG. 21 is a view showing another example of RF-signal samplingoperations according to the embodiment.

[0045]FIG. 22 is a view showing another example of RF-signal samplingoperations according to the embodiment.

[0046]FIG. 23 is a view showing another example of RF-signal samplingoperations according to the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0047] As an optical recording apparatus and a laser-power controlmethod according to an embodiment of the present invention, a disk driveapparatus (recording and reproduction apparatus) for DVD-Rs and itslaser-power control operation will be taken as examples and described.Descriptions will be given in the following order.

[0048] 1. Pulse-Train Recording Method and RF Signal

[0049] 2. Structure of Disk Drive Apparatus

[0050] 3. Recording Power Compensation Operation (Example 1)

[0051] 4. Recording Power Compensation Operation (Example 2)

[0052] 5. Recording Power Compensation Operation (Example 3)

[0053] 6. Various Modifications

[0054] 1. Pulse-Train Recording Method and RF Signal

[0055] The disk drive apparatus according to the present embodimentrecords and reproduces data into and from recording media having anorganic pigment film, such as DVDRs, and emits a laser by a so-calledpulse train method when recording.

[0056] A pulse-train-manner laser emission driving method used whenrecording and a reflected-light information signal, which is an RFsignal, observed during a recording operation with laser outputs will befirst described to explain the principle of laser-power control,described later, executed in the disk drive apparatus according to thepresent embodiment.

[0057] When recording, data to be recorded is encoded to finallygenerate an NRZI-method run-length-limited code.

[0058] For example, FIG. 1(a) shows a data track on a disk in asimplified manner. To form a data track having marks M and spaces SP inthis way, a data stream shown in FIG. 1(b) is output from an encodingsystem as encoded data.

[0059] In this case, an encoded data stream which forms a 8T mark (pit),a 3T space, a 3T mark, a 4T space, and a 6T mark is indicated (where Tmeans the unit of length corresponding to a channel bit) as an example.

[0060] For the encoded data shown in FIG. 1(b), so-calledpulse-train-manner laser driving pulses like those shown in FIG. 1(c)are generated as a signal for actually executing laser outputs.

[0061] In other words, laser driving pulses (writing pulses) having arecording level are intermittently output according to the lengths ofpits to be formed during a period in which marks M are formed, and laserdriving pulses having a reproduction level are consecutively outputduring a period corresponding to spaces SP.

[0062] Various waveforms of the laser driving pulses can be considered,and this case shows just one example. In this case, a writing pulserises about 1.5T later than when the encoded data rises, and lasts for aperiod of 1.5T. Then, writing pulses having a period of 0.5T continuewith a period of 0.5T sandwiched by adjacent writing pulses, until theencoded data falls.

[0063] Therefore, to form an 8T mark, as shown in the figure, after a1.5T reading level, a 1.5T writing pulse is output, and then, five 0.5Twriting pulses are output with 0.5T read levels sandwiched therebetween.

[0064] To form a 6T mark, after a 1.5T reading level, a 1.5T writingpulse is output, and then, three 0.5T writing pulses are output with0.5T read levels sandwiched therebetween.

[0065] To form a 3T mark, a 1.5T writing pulse output after a 1.5Treading level is sufficient for a 3T period, there is no subsequent 0.5Twriting pulses.

[0066] Since laser output is performed by such laser driving pulses,laser power increases intermittently during pit forming periods.

[0067] When such pulse-train-manner laser outputs are performed, an RFsignal detected as light reflected from the organic-pigment-film disk isas shown in FIG. 1(d).

[0068] More specifically, a first pulse has a relatively largeamplitude, a second pulse has a smaller amplitude than the first pulse,and third, fourth, and subsequent pulses have almost the same amplitudeas the second pulse.

[0069] For convenience of description, pulses observed in the RF signalare called first pulses P#1, second pulses P#2, third pulses P#3, . . ., and an n-th pulse P#n, as shown in FIG. 2.

[0070] In addition, the peak of the amplitude of a pulse is called “PK,”the bottom value thereof is called “BT,” and the center value thereof iscalled “CT.” For example, the peak of the first pulse P#1 is expressedas “PK1,” the peak of the second pulse P#2 is expressed as “PK2,” and soon.

[0071] In the same way, the bottom value “BT” and the center value “CT”of the first pulse P#1 are called “BT1” and “CT1,” the bottom value “BT”and the center value “CT” of the second pulse P#2 are called “BT2” and“CT2,” and so on.

[0072] Laser outputs usually have a relatively low level correspondingto a read level at periods where no mark M is generated on disk tracks,that is, where spaces SP are made. The level of the RF signal,corresponding to the periods of the spaces SP, namely, the quantity ofreflected light, is called “LSP.”

[0073] Further, the average of the second pulse P#2 to the n-th pulseP#n is called “av.” The average of the peak PK2 of the second pulse P#2to the peak PKn of the n-th pulse P#n is called “avPK.” The average ofthe bottom value BT2 of the second pulse P#2 to the bottom value BTn ofthe n-th pulse P#n is called “avBT.” The average of the center value CT2of the second pulse P#2 to the center value CTn of the n-th pulse P#n iscalled “avCT.”

[0074] As shown in FIG. 1 and FIG. 2, the first pulse P#1 has a largeamplitude, and the second pulse P#2 and subsequent pulses haverelatively small amplitudes in the RF signal. This is because, since thegeneration of a mark is instantaneously started by laser emission causedby the first writing pulse in laser driving pulses, the second pulse P#2and subsequent pulses in the RF signals have reduced amounts ofreflected light due to the effect of the mark being formed. Namely, theRF signal, especially the second pulse P#2 and subsequent pulses, showsinformation affected by the mark being formed. In other words, the RFsignal can be an information signal by which a mark generation state ismonitored in real time.

[0075]FIG. 3 to FIG. 6 show RF-signal waveforms observed when variouslevels of recording laser power were used.

[0076] The figures show RF signals corresponding to the total quantityof light of a main beam having a DC component. Signals obtained from anRF-signal photodetector when an optical system emits pulse-train-mannerlasers to a DVD-R are current-to-voltage converted, and amplified by anRF matrix amplifier to acquire the RF signals.

[0077] The average laser-output power was 2.24 mW in FIG. 3, 3.27 mW inFIG. 4, 3.73 mW in FIG. 5, and 4.72 mW in FIG. 6.

[0078] When the peak PK1 of the first pulse P#1 and the peaks PK2, . . ., and PKn of the second pulse P#2 and subsequent pulses in each RFsignal are observed, it is found from the experimental results that thepeaks PK2, . . . , and PKn of the second pulse P#2 and subsequent pulseswere almost not changed under a certain recording condition (adetermined recording medium, a determined optical system, and adetermined linear velocity).

[0079] It is confirmed especially from the comparison between FIG. 3 andFIG. 4 that the ratios of the peak PK1 of the first pulse P#1 and thepeaks PK2, . . . , and PKn of the second pulse P#2 and subsequent pulseswere changed according to the magnitude of the quantity of light emittedon the recording medium.

[0080] In addition, it is also found that the quality of a reproductionRF signal became best in that recording area if the ratio of the peakPK1 and the peak PK2 was a certain constant value during recording, whenthe quality was evaluated by a jitter.

[0081] From these findings, it is understood that a feedback functioncan be implemented that allows recording power most suitable forgenerating marks to be output in an environment when an RF signal ismonitored during recording; the ratio of, for example, the peak PK1 andthe peak PK2 is calculated; and if the ratio is shifted from the value(reference value measured in advance in various conditions) regarded asthat which provides the best recording condition, a compensation isgiven to a laser-power control system.

[0082]FIG. 7 shows the relationship between recording laser power andnormalized amplitudes obtained from the experiments. Normalizedamplitudes are the values obtained by dividing the amplitudes by theamplitude (peak) of the first pulse P#1, that is, the ratiotherebetween.

[0083] The figure show the peaks PK1 of the first pulses P#1, thenormalized peaks (PK2/PK1) of the second pulses P#2, the normalizedpeaks (PK3/PK1) of the third pulses P#3, the normalized bottom values(such as BT3/PK1) of the third pulses P#3 (and subsequent pulses), thenormalized center values (such as CT3/PK1) of the third pulses P#3 (andsubsequent pulses), and the normalized modulation values (such as(PK3−BT3)/PK1) of the third pulses P#3 and subsequent pulses in alaser-power range of 2 mW to 5 mW.

[0084] It is assumed that the reproduction RF signal has the bestquality in a predetermined linear-velocity condition of the system whenthe average recording power is about 2.8 mW.

[0085] For example, it can be considered that the normalized peak of thesecond pulse P#2 is reduced from 0.80 as the recording power isgradually increased, and the mark generation state becomes best when thenormalized peak is settled at about 0.63.

[0086] From this phenomenon, it is understood that, if energy requiredfor generating marks is insufficient due to an environmental temperaturechange or film unevenness on the medium, the normalized peak of thesecond pulse shows a value larger than 0.63, such as 0.70.

[0087] In other words, when the ratio (P2/P1), which is a normalizedvalue, is monitored during recording; and an instruction for increasingthe recording power to return the value to the normal value is given tothe laser control system to actually increase the laser power, thenormalized peak of the second pulse returns to 0.63, and the markgeneration condition also becomes best in the environment.

[0088] Conversely, if the energy required for generating a mark isexcessive, when the normalized amplitude of the second pulse ismonitored and a difference with the target value of 0.63 is fed back tothe laser control system, a mark is always generated in the bestcondition.

[0089] When a ratio to be detected is called B/A, the ratio (PK2/PK1)between the peak PK1 of the first pulse P#1 and the peak PK2 of thesecond pulse P#2 is used as the ratio B/A to be detected, in theforegoing description. It is understood from FIG. 7 that the normalizedpeaks, the normalized bottom values, the normalized center values, andthe normalized modulation values of the third pulse P#3 and subsequentpulses are also changed linearly to some extent in a range of, forexample, 2 mW to 3 mW (where it is assumed that there exists the mostsuitable laser power).

[0090] Therefore, it is considered that, in addition to the ratiobetween the peak PK1 of the first pulse P#1 and the peak PK2 of thesecond pulse P#2, the ratio between the peak PK1 and the peak PK3 (orPK4, . . . ), the ratio between the peak PK1 and the center value CT2(or CT3, . . . ), the ratio between the peak PK1 and the bottom valueBT2 (or BT3, . . . ), the ratio between the peak PK1 and the average av(or avPK, avCT, or avBT), the ratio between the peak PK1 and themodulation value (PK2−BT2, or PK3−BT3, . . . ), and so on can be usedfor laser-power feedback control in the same way.

[0091] When normalization is performed by using the center value CT1 ofthe first pulse P#1, it is considered that the same results areobtained. Therefore, the center value CT1 or the modulation value(PK1−BT1) may be used as the value A, instead of the peak PK1.

[0092] In other words, the ratio B/A to be detected can be PK3/PK1,BT2/PK1, CT2/PK1, avPk/PK1, or various others in addition to PK2/PK1.

[0093] Since there exists no second and subsequent pulses during a3T-mark generation period as understood from FIG. 1, the value B is notobtained. Therefore, an operation for obtaining the ration B/A is notperformed during the 3T-mark generation period.

[0094] A structure and operation according to the present embodimentwill be described later. A fundamental idea of operations is that aratio observed in the RF signal, that is, a ratio B/A, is detected,where a value A indicates a signal value (such as PK1 or CT1) related tothe first pulse, and a value B indicates a signal value (such as PK2,PK3, CT2, CT3, BT2, BT3, av, or avPK) related to the second andsubsequent pulses, and laser-power feedback control is performedaccording to the ratio, as described above (although the value A iscompensated in the present embodiment, as described later).

[0095] In the present embodiment, as in an optical recording apparatusfor organic-pigment-film recording media, it is assumed that a markgeneration speed is faster than in usual phase-change media during arecording process, and luminous flux having recording power is obtainedon an RF photodetector as reflected light from the surface of a medium,indicating the generation state of a mark to be changed by its energy,which passes through a returning path in the optical system.

[0096] It is further assumed that pulse-train-manner laser emission isemployed in order to form marks at accurate positions by avoiding heatinterference on a recording medium, in a high-density recording system.

[0097] In a so-called APC laser control method, which has been usedconventionally, an APC photodetector monitors (front monitoring) part ofoutgoing luminous flux to obtain a change caused by an environmentaltemperature change or during aging in the I-L (current and opticaloutput) characteristic of a semiconductor laser, the quantity of theoutgoing light is estimated, and the estimated quantity is compared withthe recording-power target value specified in advance to feedback thestate to a laser driving circuit system.

[0098] To accurately obtain pulse-train-manner optical-recordingwaveforms, a circuit for sampling a monitoring signal of the quantity ofoutgoing light at timing corresponding to the pulse width is required.With this, even if an environmental temperature is changed, or agingoccurs, the outgoing laser power is always maintained at a constantlevel.

[0099] This is just for controlling the laser output level so that it isthe most suitable level. Factors which affect mark generation other thanthe I-L characteristic of the semiconductor laser, such as recordingfilm unevenness or a change in the energy absorption efficiency of therecording medium caused by wavelength fluctuation due to a temperaturechange, described above, cannot be covered.

[0100] In the present embodiment, reflected light which includesmark-generation information is observed by the RF photodetector duringrecording; it is determined almost at the same time whether therecording power currently being output is most suitable for markgeneration; and if the recording power is shifted from the most suitablestate, a compensation is fed back to the laser-power control system tocontrol the power of the semiconductor laser. Therefore, laser-powercontrol which covers all factors which affect mark generation, such asrecording film unevenness or a change in the energy absorptionefficiency due to waveform fluctuation, can be implemented.

[0101] More specifically, a signal measured by the RF photodetector isobserved at timing slightly delayed with respect to thepulse-train-manner outgoing luminous flux output from the semiconductorlaser, due to a go-and-return optical length, photoelectric-conversiontime, and transmission time, in a state limited by the frequencycharacteristics of the optical system and the electrical system. Whenthe signal is sampled at suitable timing corresponding to pulse periodsto obtain the ratio between measured amplitudes, it is determinedwhether a mark has been generated successfully. In other words, when theobtained ratio is compared with a target ratio value, a feedback controlsignal is obtained for laser-power control.

[0102] As described above, the ratio B/A is detected, and laser-powerfeedback control is performed according to the ratio. This method iseffective just under a system condition in which the most appropriaterecording laser power falls in a range of 2 to 3 mW. More specifically,as understood from FIG. 7, since a change in normalized values, that is,a change in the ratio B/A, is linear in the range of 2 to 3 mW, controlfor increasing or reducing laser power according to the comparisonbetween the ratio B/A and a reference ratio is allowed.

[0103] It is found from FIG. 4, FIG. 5, and FIG. 6 that there is noconspicuous difference among the differences between the peaks of thefirst pulses P#1 and the peaks of the second pulse P#2 and subsequentpulses when the laser power is equal to or more than 3 mW.

[0104] As shown in FIG. 7, normalized values (B/A) do not show definitechanges in a zone where the laser power is equal to or more than 3 mW.Therefore, even if the ratio B/A is compared with a reference ratio, adesirable direction (increase or reduction) cannot be determined forlaser power control, and appropriate laser power control cannot be

[0105] Consequently, the above fundamental idea can be an effectivelaser-power control method in recording systems where the mostappropriate laser power falls in a range of 2 to 3 mW, but the ideaneeds to be further developed in recording systems where the mostappropriate recording laser power can be 3 mW.

[0106] With recording conditions such as a medium type, a recordingdensity, and a linear velocity being taken into account, it is necessaryto assume that there are recording systems where the most appropriaterecording laser power is 3 mW.

[0107] Based on the above-described background, it is considered that alaser-power control operation, described later, according to the presentembodiment is applied to a case in which recording is performed at ahigh linear velocity according to a system condition, and a case inwhich a write strategy is employed to have a relatively-large-widthfirst pulse. It is assumed that, when the laser power reaches the mostappropriate recording power, an effect of mark generation extends to thequantity of reflected light corresponding to the first pulse.

[0108] In the above-described fundamental idea, whether a mark has beensuccessfully generated is determined by checking the ratio B/A, wherethe value A (value not affected by a mark-generation state) indicatesthe quantity of reflected light corresponding to the first pulse P#1 andis used as a reference, and the value B (value affected by themark-generation state) indicates the quantity of reflected lightcorresponding to the second pulse P#2 and subsequent pulses. The reasonwhy the ratio B/A is not changed at 3 mW or more, for example, as shownin the experimental results of FIG. 3 to FIG. 6 is that the first pulseP#1 itself in the RF signal is affected by a pit mark generatedinstantaneously by the laser illumination corresponding to the firstpulse, and the amplitude corresponding to the reflected light issuppressed.

[0109] When the quantity of reflected light corresponding to the firstpulse P#1 in the RF signal is affected by a mark-generation state inthis way, the value A, which serves as a reference value correspondingto the quantity of light not affected by a mark, becomes indefinite, andas a result, it is difficult to indicate the state of the mostappropriate recording power only by the ratio B/A.

[0110] Therefore, in operations according to the present embodiment, avalue A′ obtained by compensating the value A, which is the quantity ofreflected light corresponding to the first pulse P#1, for a portionaffected by a mark generation, and laser power control is performedaccording to the ratio B/A′.

[0111]FIG. 8 shows the peak PK1 of the first pulse P#1 in an RF signaland a compensated peak PK1′, which indicates the peak PK1 compensated asto have no effect of mark generation, both obtained when the recordinglaser power is changed. The compensated peak PK1′ linearly changes inproportion to the recording laser power.

[0112]FIG. 8 also shows a normalized value PK2/PK1, which indicates thepeak PK2 of the second pulse P#2, normalized by the peak PK1, and acompensated normalized value PK2/PK1′, which indicates the peak PK2 ofthe second pulse P#2, normalized by the compensated peak PK1′.

[0113] It is found that the compensated normalized value PK2/PK1′ ischanged in a certain direction with respect to the recording laserpower. In other words, it is understood that, even when the laser powerbecomes equal to or larger than, for example, 3 mW, the compensatednormalized value PK2/PK1′ functions as information by which a markgeneration state can be determined.

[0114]FIG. 9 shows the characteristics of compensated normalized valuescorresponding to the normalized values shown in FIG. 7, that is, thecharacteristics obtained when the normalization reference is changedfrom the peak PK1 to the compensated peak PK1′.

[0115] It is understood from the figure that each compensated normalizedvalue shows a specific tendency with respect to changes in the recordinglaser power, and more precisely, the value is reduced as the recordinglaser power increases.

[0116] Therefore, each of compensated normalized values PK2/PK1′,PK3/PK1′, BT3/PK1′, CT3/PK1′, and (PK3−BT3)/PK1′, corresponding to theratio B/A′, can be used for the same laser power control as in theabove-described fundamental idea.

[0117] As the value B in the ratio B/A′, any of the peaks PK2, PK3, . .. , the center values CT2, CT3, . . . , the bottom values BT2, BT3, . .. , the averages, av, avPK, avCT, and avBT, the modulation values(PK2−BT2), (PK3−BT3), . . . corresponding to the second pulse P#2 andsubsequent pulses needs to be used in the same way as described in theabove fundamental idea.

[0118] As the value A′, a compensated center value CT1′ or a compensatedmodulation value (PK1−BT1)′ may be used, in addition to the compensatedpeak PK1′, obtained by compensating the peak PK1 of the first pulse P#1.

[0119] The value A′, for example, the compensated peak PK1′ of the firstpulse P#1, is obtained in the following way.

[0120] Since the compensated peak PK1′ is set to a value not affected bya mark-generation state, a value not affected by the mark-generationstate is first observed. More specifically, the amplitude of an RFsignal, corresponding to a space SP period, that is, the quantity LSPshown in FIG. 2, of reflected light needs to be detected at a spaceperiod.

[0121] The above-described APC control regulates the laser output withrespect to a recording power (corresponding to the peak of a pulsetrain) and a reproduction power (corresponding to a level at a spaceperiod), both specified as laser power.

[0122] When the quantity LSP of reflected light is detected at a spaceperiod as a value not affected by the mark-generation state, thequantity of reflected light, which serves as a value not affected by themark-generation state, that is, the compensated peak PK1′, can beestimated by using a specified ratio between the recording powerspecified in the APC system and a power at a space area.

[0123] Since a first-pulse waveform is observed as a slightly droopedwaveform due to the optical pickup, the state of a recording medium, andthe restrictions of the frequency characteristics of electric circuitsystems, when calibration is performed at a low recording power statewhere the quantity of reflected light corresponding to the first pulseP#1 is obviously not affected by mark generation, the compensated peakPK1′ serving as a more precise reference value can be obtained in somecases.

[0124] When the compensated peak PK1′ obtained in this way is used asthe value A′ and the ratio B/A′ is calculated, even if the recordinglaser power becomes high to some extent, only the changes caused by markgeneration, of the quantities of reflected light corresponding to thesecond pulse P#2 and subsequent pulses can be taken while the changesare not affected by the change caused by an organic-pigment filmunevenness on the control medium, of the quantity of the entirereflected light.

[0125] Therefore, when the shift of the detected ratio B/A′ against atarget ratio between the value A′ and the value B, indicating the mostappropriate recording state and obtained in advance correspondingly tovarious recording conditions, is calculated and fed back to the lasercontrol system, even if the first pulse P#1 in an RF signal is affectedby mark generation, the most appropriate recording power for markgeneration can be obtained precisely.

[0126] 2. Structure of Disk Drive Apparatus

[0127] A specific structure and operation according to the presentembodiment will be described below.

[0128] A disk drive apparatus serving as an embodiment of an opticalrecording apparatus according to the present invention is, for example,an apparatus for recording and reproducing data into and from DVD-Rs.Compensation control with the ratio (B/A′) of sample values of an RFsignal, as described above, is performed in addition to APC control inlaser-power control. It is assumed in the most fundamental processingthat the ratio between the compensated peak PK1′ of the first pulse P#1and the peak PK2 of the second pulse P#2 is used as the ratio (B/A′),where PK1′ serves as the value A and PK2 serves as the value B.

[0129] Various other ratios can be used, and they will be describedlaser in modifications.

[0130]FIG. 10 shows the entire structure of a disk drive apparatus 30according to the present embodiment. FIG. 11 illustrates the structureof a main part related to laser-power control in the structure shown inFIG. 10.

[0131] As shown in FIG. 10, a disk 100, such as a DVD-R, is mounted on aturntable 7, and rotated by a spindle motor 6 at a constant linearvelocity (CLV) in a recording/reproduction operation.

[0132] An optical pickup 1 reads pit data recorded in tracks, trackwobbling information, and land-prepit information. Pits recorded as dataon tracks formed as grooves are so-called pigment-change pits.

[0133] In the pickup 1, a laser diode 4 serving as a laser light source,a photodetector 5 for detecting reflected light, an objective lens 2serving as an output end of laser light, and an optical system 24 forilluminating a disk recording surface through the objective lens 2 andfor leading reflected light therefrom to the photodetector 5 areprovided.

[0134] A monitor detector 22 for receiving part of the output light fromthe laser diode 4 is also provided therein.

[0135] The structure inside the pickup 1 is shown in FIG. 11 in anoutlined manner. Laser light output from the laser diode 4 is led to theobjective lens 2 by the optical system 24, which has a grating plate(not shown), a collimator lens 24 a, a retardation plate (not shown), aPBS (polarized beam splitter) 24 b, and a multi-lens (not shown), and isemitted on the disk 100. Light reflected therefrom is detected by thephotodetector 5.

[0136] Part of the laser light output from the laser diode 4 is also ledto the monitor detector 22, and its detection light is used for an APCoperation, described later.

[0137] The laser diode 4 outputs laser light having a wavelength of 650nm or 635 nm. The optical system has an NA of 0.6.

[0138] The objective lens 2 is held by a two-axis mechanism 3 in amovable manner in a tracking direction and a focus direction.

[0139] The pickup 1 is held by a sled mechanism 8 in a movable manner ina disk radius direction as a whole.

[0140] The laser emission of the laser diode 4 of the pickup 1 is drivenby a driving signal (driving current) sent from a laser driver 18.

[0141] As shown in FIG. 10, the information of light reflected from thedisk 100 is detected by the photodetector 5, converted to an electricsignal corresponding to the quantity of received light, and sent to amatrix circuit 9.

[0142] The matrix circuit 9 is provided with a current-to-voltageconversion circuit and a matrix calculation/amplification circuit forthe output current of a plurality of light receiving elements serving asthe photodetector 5, and generates necessary signals by matrixcalculation processing.

[0143] For example, an RF signal corresponding to reproduced data, afocus-error signal FE for servo control, and a tracking-error signal TEare generated.

[0144] In addition, a push-pull signal P/P related to wobbling of landprepits and grooves is generated.

[0145] The RF signal output from the matrix circuit 9 is sent to abinarizing circuit 11, the focus-error signal FE and the tracking-errorsignal TE are sent to a servo circuit 14, and the push-pull signal P/Pis sent to an address decoder 26.

[0146] The RF signal is also sent to a pulse sampling section 25, and isused for processing for laser-power compensation control, describedlater.

[0147] The address decoder 26 uses the push-pull signal P/P to extractland-prepit information, to generate a wobbling clock synchronized withtrack wobbling, and to decode address information pre-formatted on thedisk 100. The decoded address information is sent to a system controller10.

[0148] The generated wobbling clock is sent to the address decoder 26and to a spindle servo circuit 23. An encoding clock is generated fromthe wobbling clock, and sent to a encoding/decoding section 12.

[0149] The RF signal obtained by the matrix circuit 9 is binarized inthe binarization circuit 11, and sent to the encoding/decoding section12.

[0150] The encoding/decoding section 12 is provided with a functionalblock serving as a decoder during reproduction and a functional blockserving as an encoder during recording.

[0151] During reproduction, demodulation processing for therun-length-limited code, error correction processing, deinterleaving areperformed as decoding processing to obtain reproduced data.

[0152] The encoding/decoding section 12 generates a reproduction clocksynchronized with the RF signal by a PLL process, and executes theabove-described decoding processing with the reproduction clock, duringreproduction.

[0153] During reproduction, the encoding/decoding section 12 accumulatesdata decoded as described above in a buffer memory 20.

[0154] As a reproduction output of the disk drive apparatus 30, the databuffered in the buffer memory 20 is read and sent.

[0155] An interface section 13 is connected to an external host computer80, and performs communications with the host computer 80 for recordingdata, reproduction data, and various types of commands.

[0156] During reproduction, the reproduction data decoded and stored inthe buffer memory 20 is sent to the host computer 80 through theinterface section 13.

[0157] A read command, a write command, and other signals are sent fromthe host computer 80 to the system controller 10 through the interfacesection 13.

[0158] During recording, the host computer 80 sends recording data. Therecording data is sent from the interface section 13 to the buffermemory 20 and buffered therein.

[0159] In this case, the encoding/decoding section 12 executes encodingprocessing which includes error-correction-code addition, interleaving,sub-code addition, and run-length-limited code modulation for recordingdata for the disk 100, as encoding processing for the buffered recordingdata.

[0160] The encoding/decoding section 12 uses an encoding clocksynchronized with the wobbling clock, as a reference clock for theencoding processing.

[0161] NRZI-format recording data generated in the encoding processingexecuted by the encoding/decoding section 12 is converted topulse-train-manner recording pulses (Laser driving pulses) by a writestrategy 21, and sent to the laser driver 18.

[0162] The write strategy 21 also executes recording compensation,namely, fine adjustment of the most suitable recording power andadjustment of a laser-driving-pulse waveform according to thecharacteristics of a recording layer, the spot shape of the laser light,and a recording linear velocity.

[0163] The laser driver 18 gives driving current according to thereceived laser driving pulses to the laser diode 4 for laser emissiondriving. With this, pit marks (pigment change pits) are formed on thedisk 90 according to recording data.

[0164] An APC circuit (auto power control) 19 is a circuit section forcontrolling the laser output such that it is constant irrespective ofthe temperature while monitoring the laser output power by the output ofthe monitor detector 22. The target value of the laser output is givenby the system controller 10, and the APC circuit controls the laserdriver 18 such that the laser output level has the target value.

[0165] A detailed example structure of the APC circuit will be describedlater by referring to FIG. 11.

[0166] The servo circuit 14 generates various servo driving signals, afocus driving signal, a tracking driving signal, and a sled drivingsignal, from the focus-error signal FE and the tracking error signal TEsent from the matrix circuit 9, and executes a servo operation.

[0167] More specifically, the servo circuit 14 generates the focusdriving signal FD and the tracking driving signal TD according to thefocus-error signal FE and the trackingerror signal TE, and sends them toa two-axis driver 16. The two-axis driver 16 drives a focus coil and atracking coil in the two-axis mechanism 3 of the pickup 1. With this, atracking servo loop and a focus servo loop are generated by the pickup1, the matrix circuit 9, the servo circuit 14, the two-axis driver 16,and the two-axis mechanism 3.

[0168] The servo circuit 14 also turns off the tracking servo loop andoutputs a jump driving signal to the two-axis driver 16 in response to atrack jump instruction sent from the system controller 10 to execute atrack jump operation.

[0169] The servo circuit 14 further generates the sled driving signalaccording to a sled-error signal obtained as a low-frequency componentof the tracking-error signal TE and access execution control made by thesystem controller 10, and sends the signal to a sled driver 15. The sleddriver 15 drives the sled mechanism 8 according to the sled drivingsignal. The sled mechanism 8 includes a mechanism, although not shown,formed of a main shaft for holding the pickup 1, a sled motor, and atransmission gear. When the sled driver 15 drives the sled mechanism 8according to the sled driving signal, predetermined slide movement ofthe pickup 1 is performed.

[0170] The spindle servo circuit 23 performs control so as to CLV rotatethe spindle motor 6.

[0171] The spindle servo circuit 23 obtains the wobbling clock as theinformation of the current rotation speed of the spindle motor 6 whendata recording, and compares it with CLV reference speed information togenerate a spindle-error signal SPE.

[0172] Since the reproduction clock (clock serving asdecoding-processing reference) generated by the PLL in theencoding/decoding section 12 serves as the information of the currentrotation speed of the spindle motor 6 when data reproduction, the clockis compared with the predetermined CLV reference speed information togenerate a spindle-error signal SPE.

[0173] The spindle servo circuit 23 sends a spindle driving signalgenerated according to the spindle-error signal SPE to a spindle motordriver 17. The spindle motor driver 17 applies, for example, athree-phase driving signal to the spindle motor 6 according to thespindle driving signal to CLV rotate the spindle motor 6.

[0174] The spindle motor 23 also generates a spindle driving signalaccording to a spindle kick/brake control signal sent from the systemcontroller 10, and makes the spindle 6 perform operations, for example,start rotating, stop rotating, accelerate rotating, or deceleraterotating by using the spindle motor driver 17.

[0175] The above-described various operations in the servo systems andthe recording and reproduction system are controlled by the systemcontroller 10 formed of a microcomputer.

[0176] The system controller 10 executes various types of processingaccording to commands sent from the host computer 80.

[0177] When the host computer 80 sends a read command which requests thetransmission of data recorded in the disk 100, for example,seek-operation control is first performed with a specified address beingset to the target. More specifically, an instruction is sent to theservo circuit 14 to make the pickup 1 perform an access operation withthe address specified by a seek command being set to the target.

[0178] Then, operation control required for sending data in a specifieddata area to the host computer 80 is performed. In other words, therequired data is read from the disk 100, decoded, buffered, and sent.

[0179] When the host computer 80 sends a write command, the systemcontroller 10 first moves the pickup 1 to an address where data is to bewritten. Then, the system controller 10 makes the encoding/decodingsection 12 apply the encoding processing to the data sent from the hostcomputer 80, as described above.

[0180] Laser driving pulses are sent from the write strategy 21 to thelaser driver 18, as described above, to perform recording.

[0181] A memory 27 collectively indicates a ROM, a RAM, and anon-volatile memory used by the system controller 10 for processing. Thememory 27 may be a memory built in the system controller 10, formed ofthe microcomputer.

[0182] The memory 27 is used as a working area for calculations andstorage of a program, various coefficients, and constants required for acontrol operation in the disk drive apparatus. In the presentembodiment, various system conditions (such as a medium type and alinear velocity) and the ratios (PK2/PK1′) most suited thereto arestored in a non-volatile area of the memory 27 as information for alaser-power compensation operation, described later. For example, themost suitable ratios are experimentally obtained under various systemconditions before the apparatus is shipped from the factory, and theexperimental results are stored as a data table.

[0183] In summary, the reproduction operation and the recordingoperation of the disk drive apparatus 30 can be described as follows:

[0184] <Reproduction Operation>

[0185] Servo Operation

[0186] A signal detected by the pickup 1 is converted to servo-errorsignals, such as the focus-error signal FE and the tracking-error signalTE, in the matrix circuit 9, and sent to the servo circuit 14. Thedriving signals FD and TD output from the servo circuit 14 drive thetwo-axis mechanism 3 of the pickup 1 to perform focus servo and trackingservo.

[0187] Data Reproduction

[0188] A signal detected by the pickup 1 is converted to an RF signal inthe matrix circuit 9, and sent to the encoding/decoding section 12. Theencoding/decoding section 12 reproduces a channel clock and performsdecoding according to the channel clock. Decoded data is sent to theinterface section 13.

[0189] Rotation Control

[0190] The channel clock reproduced by the encoding/decoding section 12is sent to the spindle servo circuit 23, and the rotation of the disk100 is controlled thereby.

[0191] Address Reproduction

[0192] An address is included in the RF signal, decoded by theencoding/decoding section 12, and sent to the system controller 10.

[0193] Laser Control

[0194] The APC circuit 19 performs control so as to maintain a constantlaser output, according to an instruction of the system controller 10.

[0195] <Recording Operation>

[0196] Servo Operation

[0197] The same operation as in reproduction is performed. The matrixcircuit 9 or the servo circuit 14 performs compensation such that anincrease in gain caused by an increase in laser power does not occur.

[0198] Data Recording

[0199] Channel coding, such as ECC addition, re-arrangement, andmodulation, is applied by the encoding/decoding section 12 to datareceived through the interface section 13. The data, to which thechannel coding has been applied, is converted to laser driving pulsessuited to the disk 100 in the write strategy 21, and applied to thelaser diode 4 of the pickup 1 through the laser driver 18 (APC circuit19).

[0200] Rotation Control

[0201] The wobbling clock is generated from the push-pull signal P/Poutput from the matrix circuit 9, sent to the spindle servo circuit 23,and used for constant-linearvelocity (CLV) rotation control.

[0202] Address Reproduction

[0203] The land-prepit information is detected from the pushpull signalP/P output from the matrix circuit 9. The detected land-prepitinformation is decoded to generate an address, and read by the systemcontroller 10.

[0204] The encoding clock is also generated from the push-pull signalP/P, and sent to the encoding/decoding section 12.

[0205] A structure used for laser-power control in the presentembodiment will be described below by referring to FIG. 11. Sincelaser-power compensation performed during recording is a point inoperations in the present embodiment, the following description will bemade for recording operations.

[0206] As it is understood from the above description made by referringto FIG. 10, when laser driving pulses, that is, a combination pattern ofa specified laser-driving-current value and a modulated signal, areinput to the laser driver 18 from the write strategy 21 duringrecording, the laser diode 4 emits laser light, and the objective lens 2condenses the laser light as an optical spot and projects at apredetermined area on the disk 100 through the above-described opticalsystem 24.

[0207] The detector 22 for front monitoring receives part of outgoingluminous flux, and detects the quantity of light to estimate thequantity of the emitted light of laser power.

[0208] The luminous flux condensed on the disk 100 is returned to theoptical system 24 as reflected light (reproduction signal) whilereflecting a mark generation state on the disk, and finally projected onthe RR-signal photodetector 5 divided into multiple pieces.

[0209] The APC circuit 19 includes, for example, a current/voltageconversion section 19 a, a sample/hold circuit 19 b, an A/D converter 19c, a laser-power controller 19 d, a target-value holding section 19 e, aD/A converter 19 f, and a timing generator 19 g, as shown in FIG. 11.

[0210] The timing generator 19 g outputs various timing signalsaccording to encoded data, namely, a signal serving as the source oflaser driving pulses, output from the encoding/decoding section 12 tocontrol the operation timing of the sample/hold circuit 19 b, the A/Dconverter 19 c, and the laser-power controller 19 d.

[0211] Pulse-train-manner laser emission is performed during recording.The APC circuit 19 monitors recording-level laser power to maintain itat the target value.

[0212] A signal (current corresponding to the quantity of receivedlight) sent from the monitor detector 22 is converted to a voltage atthe current/voltage conversion section 19 a, and sent to the sample/holdcircuit 19 b. Since pulse-train-manner laser emission is performed, thesample/hold circuit 19 b samples and holds the signal at for periodwhere a pulse-train pulse width is maintained, namely, a period where arecording-power laser output is applied, at appropriate timing accordingto a timing signal sent from the timing generator 19 g.

[0213] The voltage held and output is converted to a digital value bythe A/D converter 19 c, and sent to the laser-power controller 19 d asthe current estimated laser power.

[0214] The laser-power controller 19 d compares a laser-power targetvalue specified in the target-value holding section 19 e with theestimated laser power to superpose the quantity corresponding to thedifference therebetween onto the current indication, and sends it to thelaser driver 18 through the D/A converter 19 f. The system controller 10sets a target laser-power value in the target-value holding section 19e.

[0215] With such an operation in the APC circuit 19, a function formaintaining the laser output power at the target value is obtained.

[0216] As described before, the operation performed by the APC circuit19 is to control the laser output at a constant level, and does notoptimize the recording power with factors, such as laser-wavelengthfluctuation and recording-film unevenness, being taken into account.

[0217] In the present embodiment, a structure for laser-powercompensation is further provided. More specifically, an RF signal issampled to obtain a ratio, and laser-power compensation is performedaccording to the ratio.

[0218] As shown in FIG. 11, the matrix circuit 9 is provided with acurrent/voltage conversion section 9 a and an RF matrix amplifier 9 b asa structure for obtaining an RF signal. With these components, an RFsignal is generated according to the quantity of reflected lightdetected by the photodetector 5.

[0219] The RF signal obtained in the matrix circuit 9 is sent to thepulse sampling section 25. The pulse sampling section 25 performssampling required for calculating the ratio.

[0220] In the present embodiment, it is assumed that the ratio B/A′obtained for the RF signal is set to the ratio PK2/PK1′ between thecompensated peak PK1′ of the first pulse P#1 and the peak PK2 of thesecond pulse P#2.

[0221] The compensated peak PK1′ is obtained from the quantity LSP ofreflected light detected in the RF signal, corresponding to a spaceperiod, as described above, and the setting ratio between therecording-power target value and the reproduction-power target value,specified in the APC circuit 19.

[0222] Therefore, the pulse sampling section 25 is configured such thatthe quantity LSP of reflected light is sampled in the RF signal. Astructure for sampling the peak PK2 as the value B is also provided.

[0223] More specifically, a peak holding circuit 25 a2 and an A/Dconverter 25 b 2 corresponding to the peak PK2 of the second pulse P#2,and a sample-and-hold circuit 25 d for performing sampling at a spaceperiod and an A/D converter 25 e are provided. In addition, a timinggenerator 25 c is also provided.

[0224] To obtain the compensated peak PK1′ of the first pulse P#1, it isnecessary to obtain at least the quantity LSP of reflected light at aspace period. When the peak PK1 of the first pulse P#1 is actuallyobtained, the compensated peak PK1′ can be corrected to a further moreappropriate value. To this end, as shown in the figure, a peak holdingcircuit 25 a1 and an A/D converter 25 b1 corresponding to the peak PK1of the first pulse P#1 are also provided.

[0225] The timing generator 25 c sends a signal shown in FIG. 12(d),which indicates a sampling period corresponding to a period of the firstpulse P#1 in an RF signal shown in FIG. 12(c), to the peak holdingcircuit 25 a1 according to the encoded data shown in FIG. 12(a) sentfrom the encoding/decoding section 12 to hold and output the peak duringthe period. The timing generator 25 c also applies timing control to theA/D converter 25 b1 so as to convert the held and output peak to adigital value.

[0226] The timing generator 25 c further sends a signal shown in FIG.12(e), which indicates a sampling period corresponding to a period ofthe second pulse P#2 in the RF signal, to the peak holding circuit 25 a2to hold and output the peak during the period. The timing generator 25 calso applies timing control to the A/D converter 25 b 2 so as to convertthe held and output peak to a digital value.

[0227] The timing generator 25 c further sends a signal shown in FIG.12(f), which indicates a sampling period corresponding to a space periodin the RF signal to the sample-and-hold circuit 25 d at a point of time,such as when a laser-power compensation operation is started, to holdand output the peak in the period. The timing generator 25 c alsoapplies timing control to the A/D converter 25 e so as to convert theheld and output peak to a digital value.

[0228] With these operations, the A/D converter 25 b1 outputs the peakPK1 as the digital value, and the A/D converter 25 b 2 outputs the peak2 as the digital value. In addition, the A/D converter 25 e outputs thequantity LSP of reflected light as the digital value. Each digital valuecan be sent to the system controller 10 at a necessary point of time.

[0229] Since the pulse-train-manner laser driving pulses shown in FIG.12(b) are generated according to the encoded data shown in FIG. 12(a),the timing generator 25 c can obtain the timing of the first-pulse P#1period, the second-pulse P#2 period, and the space period in the RFsignal shown in FIG. 12(c) from the encoded data. Actually, there is adelay caused by processing in the optical system 24 and the matrixcircuit 9 between laser-output timing and timing when the pulse samplingsection 25 receives the RF signal, which is reflected-light information.Therefore, the timing generator 25 c generates timing signals forsampling periods with the delay being taken into account.

[0230] The system controller 10 reads the peaks PK1 and PK2 and thequantity LSP of reflected light at the space period, calculates theratio, and compares the calculated ratio with a reference ratio togenerate a laser-power compensation signal.

[0231] In FIG. 11, functional blocks for generating such a laser-powercompensation signal are shown inside the system controller 10.

[0232] A sampled-value input section 10 a, an estimation calculationsection 10 b, a compensation calculation section 10 c, acompensation-reference holding section 10 d, and acompensated-first-pulse-value estimation section 10 e are provided.Actually, these sections need to be implemented by software in thesystem controller 10.

[0233] Detailed processing examples will be described by referring toFIG. 13 and FIG. 14. The sampled-value input section 10 a reads the peakPK2 as the value B, and sends it to the estimation calculation section10 b. When the sampled-value input section 10 a reads the peak PK1 andthe quantity LSP of reflected light at the space period, thesampled-value input section 10 a sends them to thecompensated-first-pulse-value estimation section 10 e as information forobtaining the compensated peak PK1′ (value A′).

[0234] The compensated-first-pulse-value estimation section 10 eassociates the quantity LSP of reflected light at the space period withthe ratio of (recording power)/(reproduction power) in the APC circuit19, that is, the target ratio which the system controller 10 hasspecified for the APC circuit 19, to estimate the peak PK1′ (value A′)not affected by mark generation, of the first pulse P#1.

[0235] The compensated-first-pulse-value estimation section 10 e alsocorrects the estimated peak PK1′ by using the received peak PK1.

[0236] The estimation calculation section 10 b uses the peak PK2 sentfrom the sampled-value input section 10 a as the value B and thecompensated peak PK1′ sent from the compensated-first-pulse-valueestimation section 10 e as the value A′ to calculate a ratio, that is,B/A′ (PK2/PK1′), as an estimate of the current laser power.

[0237] The compensation-reference holding section 10 d holds the mostappropriate PK2/PK1′ value (hereinafter called a reference ratio)corresponding to the current recording conditions, including the currentlinear velocity. For example, among the most appropriate ratios forrecording conditions, stored in the memory 27 shown in FIG. 10 as thetable, as described above, the most appropriate ratio corresponding tothe current conditions has been loaded.

[0238] The compensation calculation section 10 c compares the ratiocalculated by the estimation calculation section 10 b with the referenceratio held by the compensation-reference holding section 10 d togenerate the laser-power compensation signal.

[0239] The laser-power compensation signal is sent to the laser-powercontroller 19 d in the APC circuit 19. The laser-power controller 19 dcompensates, for example, the target value stored in the target-valueholding section 19 e and used for the laser-power regulation control,described above, according to the laser-power compensation signal.

[0240] The target value itself stored in the target-value holdingsection 19 e may be updated by the laser-power compensation signal.

[0241] With such a structure, in the present embodiment, the ratioserving as a recording-power estimate is calculated almost at the sametime when recording, from the correlation of the amplitudes of the RFsignal corresponding to the pulse-train-manner waveform. The ratio iscompared with the reference ratio to calculate a value used forcompensating the recording power. The operation in the APC loop iscompensated. With this, feedback for most-appropriate recording-powercontrol is implemented with a mark generation state on the disk 100being taken into account.

[0242] 3. Recording-Power Compensation Operation

EXAMPLE 1

[0243] A specific example of the laser-power compensation processingperformed in the system controller 10, that is, the processing executedby the functional blocks shown in FIG. 11 inside the system controller10, will be described by referring to FIG. 13.

[0244] Steps shown in FIG. 13 correspond to the functional blocks shownin FIG. 11 as follows:

[0245] F101 and F104: Compensation-reference holding section 10 d

[0246] F102, F103, and F107: Compensated-first-pulse-value estimationsection 10 e

[0247] F105 and F106: Sampled-value input section 10 a

[0248] F108: Estimation calculation section 10 b

[0249] F109 to F112: Compensation calculation section 10 c

[0250] In the recording-laser-power compensation processing, the systemcontroller 10 first checks various system conditions related to arecording operation in step F101. More specifically, the systemcontroller 10 checks a medium type, a recording linear velocity, and arecording-power target value.

[0251] Next, in step F102, the system controller 10 reads the quantityLSP of reflected light at the space period from the pulse samplingsection 25.

[0252] Then, in step F103, the system controller 10 calculates thecompensated peak PK1′, that is, the value A′, from the quantity LSP ofreflected light and a system condition (specified ratio between therecording-power target value and the reproduction-power target value).

[0253] In step F104, a reference ratio (B/A′)ref suited to the systemconditions checked in step F101 is read from the data table stored inthe memory 27.

[0254] With this, a preparation for the compensation processing has beenfinished, and a compensation calculation process starts at step F105.

[0255] In step F105, the peak PK1 of the first pulse P#1 output from theA/D converter 25 b1 is read.

[0256] In step F106, the peak PK2 of the second pulse P#2 output fromthe A/D converter 25 b 2 is read as the value B.

[0257] In step F107, the compensated peak PK1′ (value A1) calculated instep F103 is corrected by using the peak PK1 read in step F105. Thiscorrection is made for non-uniform reflectivity on the disk 90.

[0258] For example, the peak PK1 of the first pulse P#1 in the RF signalis changed with respect to the recording laser power as shown in FIG. 8.Therefore, the peak PK1 can be estimated from the current recordinglaser power according to the characteristic shown in FIG. 8. If there isa difference between the estimated peak PK1 and the peak PK1 actuallydetected, it can be determined that the difference is caused bynon-uniform reflectivity of the disk.

[0259] Consequently, the estimated compensated peak PK1′ can be adjustedto a value in which the non-uniform reflectivity is taken into accountwhen the compensated peak PK1′ is multiplied by the ratio correspondingto the difference.

[0260] In step F108, the ratio B/A′ is calculated.

[0261] In step F109, the calculated ratio B/A′ is compared with thereference ratio (B/A′)ref.

[0262] When the ratio B/A′ is larger than the reference value (B/A′)ref,the processing proceeds to step F111, and the value obtained byincreasing the current recording-power target value, that is, therecording-power target value held by the target-value holding section 19e of the APC circuit 19, by 0.5 mW is set to a new compensatedrecording-power target value.

[0263] Then, in step F112, the new recording-power target value is sentto the laser-power controller 19 d as a laser-power compensation signal,and the APC loop is made to execute laser power control by using the newrecording-power target value. Then, the processing returns to step F105.

[0264] When the ratio B/A′ is smaller than the reference value (B/A′)refin step F109, the processing proceeds to step F110, and the valueobtained by reducing the current recording-power target value, that is,the recording-power target value held by the target-value holdingsection 19 e of the APC circuit 19, by 0.5 mW is set to a newcompensated recording-power target value.

[0265] Then, in step F112, the new recording-power target value is sentto the laser-power controller 19 d as a laser-power compensation signal,and the APC loop is made to execute laser power control by using the newrecording-power target value. Then, the processing returns to step F105.

[0266] After the processing returns to step F105, the same processes arerepeated.

[0267] In summary, the ratio B/A′ is compared with the reference ratio(B/A′)ref, and the recording-power target value in the APC loop isincreased or reduced by 0.5 mW at a time such that the ratio B/A′converges almost at the reference ratio (B/A′)ref.

[0268] When the ratio B/A′ becomes almost equal to the reference ratio(B/A′)ref at a point of time in step F106, therecording-power-target-value compensation processing is terminated.

[0269] As described above, according to the processing example shown inFIG. 13, the recording-power target value used as the reference in theAPC circuit 19 is compensated according to the comparison between theratio B/A′ and the reference value (B/A′)ref such that the ratio B/A′finally matches the reference ratio (B/A′)ref, that is, the recordinglaser power reaches the most appropriate recording laser power.

[0270] With such laser-power compensation processing being performed,the actual recording power is controlled so as to be most appropriatefor the current recording-operation environment. With this, the laseroutput can be controlled for laser wavelength fluctuation due to thetemperature dependency of the I-L characteristic of the laser diode 4 oraging, a change in the energy absorption efficiency of the disk 100 duethereto, and a change in the most appropriate recording power due to thefilm unevenness of the disk 100. Therefore, the most appropriatemark-generation operation is implemented, and the quality (jitter andothers) of an RF signal is improved when reproduction.

[0271] Further, non-uniform reflectively is also handled, and the mostappropriate control is allowed.

[0272] 4. Recording-Power Compensation Operation

EXAMPLE 2

[0273]FIG. 14 shows a processing example which can be employed in steadof that shown in FIG. 13, as recording-power compensation processing.

[0274] Since steps F201 to F208 are the same as steps F101 to F108 shownin FIG. 13, a description thereof is omitted.

[0275] In the processing example shown in FIG. 14, after the ratio B/A′is calculated in step F208, (B/A′)/(B/A′)ref is calculated in step F209.

[0276] Then, in step F210, it is determined whether (B/A′)/(B/A′)ref is“1” or not. When it is not “1” (does not fall in an area where it isregarded as “1”), the processing proceeds to step F211.

[0277] In step F211, a ratio α corresponding to the shift of the ratioB/A′ against the reference ratio (B/A′)ref is calculated.

[0278]FIG. 15 shows the relationship between the recording power, andthe ratio B/A′ and the reference ratio (B/A′)ref obtained from the tabledata. Under the current system conditions, it is assumed that recordingpower Pref shown in the figure is the most appropriate. In this case,according to the calculated ratio B/A′, the current power is estimatedas recording power Po shown in the figure with the system conditionsbeing taken into consideration.

[0279] In the above description, the ratio a is specified inPref=(1+α)Po, and indicates the increase ratio of the currentrecording-power target value to the new compensated recording-powertarget value.

[0280] The ratio α satisfies, for example, −0.3≦α≦0.3.

[0281] After the ratio α is calculated, the value obtained bymultiplying the current recording-power target value, that is, therecording-power target value held by the target-value holding section 19e of the APC circuit 19, by (1+α) is set to a new compensatedrecording-power target value in step F212.

[0282] Then, in step F213, the new recording-power target value is sentto the laser-power controller 19 d as a laser-power compensation signal,and the APC loop is made to execute laser power control by using the newrecording-power target value. The processing returns to step F205.

[0283] In such compensation processing, if algorithm used forcalculating the ratio a for compensation is ideal and therecording-power target value reaches the most appropriate value by onecompensation operation, the processing may be finished at step F213.When a condition that the algorithm is not always ideal is taken intoaccount, however, it is preferred that the processing return to stepF205, the determination at step S210 be repeated, and the compensationprocessing be finished after it is confirmed that the laser powersufficiently approaches the most appropriate state, that is,(B/A′)/(B/A′)ref reaches “1” (or falls in an area in which it isregarded as “1”).

[0284] Even with such laser-power compensation processing, the laseroutput can be controlled for a change in the energy absorptionefficiency of the disk 100 due laser wavelength fluctuation and a changein the most appropriate recording power due to the film unevenness ofthe disk 100. Therefore, the most appropriate mark-generation operationis implemented, and the quality (jitter and others) of an RF signal isimproved when reproduction.

[0285] 5. Recording-Power Compensation Operation

EXAMPLE 3

[0286] A still another example of a recording-power compensationoperation will be described by referring to FIG. 16 and FIG. 17.

[0287] In the processing examples shown in FIG. 13 and FIG. 14, theestimated compensated peak PK1′, serving as the value A, is corrected byusing the peak PK1 actually detected.

[0288] When the non-uniformity of reflectivity on the disk 100 is notlarge or is as small as it can be ignored, it is not necessary tofurther correct the estimated compensated peak PK1′ according to thedetected peak PK1.

[0289] The processing example shown in FIG. 17 omits such correction ofthe compensated peak PK1′.

[0290] Therefore, since it is not necessary to detect the peak PK1 inthis case, the pulse sampling section 25 has a structure shown in FIG.16. In other words, the peak holding circuit 25 a 1 and the A/Dconverter 25 b 1 corresponding to the first pulse P#1 are omitted fromthe structure shown in FIG. 11.

[0291] In addition, the sampled-value input section 10 a of the systemcontroller 10 needs to send the received peak PK2 of the second pulseP#2 to the estimation calculation section 10 b as the value B, and needsto send the received quantity LSP of reflected light at a space periodto the compensated-first-pulse-value estimation section 10 e.

[0292] A flowchart shown in FIG. 17 indicates the processing shown inFIG. 14 from which the steps F205 and F207 are omitted.

[0293] More specifically, steps F301 to F304 in FIG. 17 are the same assteps F201 to F204 shown in FIG. 14.

[0294] Step F305 in FIG. 17 is the same as step F206 in FIG. 14.

[0295] In addition, steps F306 to F311 in FIG. 17 are the same as stepsF208 to F213 shown in FIG. 14.

[0296] Since the process of each step in FIG. 17 overlaps with that inFIG. 14, a description thereof is omitted.

[0297] According to such a processing example, the simplified structureof the pulse sampling section 25 and a reduction in the processing loadof the system controller 10 are obtained as advantages, in addition tolaser-power optimization.

[0298] 6. Various Modifications

[0299] The disk drive apparatus 30 and the laser-power compensationoperation thereof have been described in the embodiment. The presentinvention is not limited to the above embodiment, and variousmodifications can be considered.

[0300] In the above-described embodiment, the compensated peak PK1′obtained by compensating the peak PK1 of the first pulse P#1 serves asthe value A′, the peak PK2 of the second pulse P#2 is sampled and usedas the value B, and PK2/PK1′ is used as the ratio B/A′.

[0301] However, the ratio B/A′ is not limited to this ratio, and can beother various ratios as described above.

[0302] For example, when the average avPK of the peaks of the secondpulse P#2 and subsequent pulses is used as the value B, the pulsesampling section 25 needs to be configured as shown in FIG. 18.

[0303] More specifically, in this case, the pulse sampling section 25 isprovided with a sample-and-hold circuit 25 d and an A/D converter 25 eas a structure for obtaining the quantity LSP of reflected light at aspace period, used for estimating the value A′.

[0304] The pulse sampling section 25 is also provided with a peakholding circuit 25 a 2 and an A/D converter 25 b 2 corresponding to thepeak PK2, a peak holding circuit 25 a 3 and an A/D converter 25 b 3corresponding to the peak PK3, . . . , and a peak holding circuit 25a(n) and an A/D converter 25 b(n) corresponding to the peak PKn areprovided as structures for sampling the peaks PK2, PK3, . . . , and PKnof the second pulse P#2 and subsequent pulses, which are used forobtaining the average avPK as the value B.

[0305] When the peak PK1 of the first pulse P#1 is sampled to adjust thevalue A1 as shown in FIG. 13 and FIG. 14, a peak holding circuit 25 a 1and an A/D converter 25 b 1 corresponding to the peak PK1 are provided.When the processing shown in FIG. 17 is employed, however, the peakholding circuit 25 al and the A/D converter 25 b 1 are unnecessary.

[0306] The timing generator 25 c sends a signal shown in FIG. 19(d),indicating a sampling period corresponding to a period of the firstpulse P#1 in an RF signal shown in FIG. 19(c) according to encoded datashown in FIG. 19(a) sent from an encoding/decoding section 12, to thepeak holding circuit 25 a 1 to hold and output the peak in the period.In addition, the timing generator 25 c performs timing control such thatthe A/D converter 25 b 1 converts the held and output peak to a digitalvalue.

[0307] The timing generator 25 c also sends a signal shown in FIG.19(e), indicating a sampling period corresponding to a period of thesecond pulse P#2 in the RF signal to the peak holding circuit 25 a 2 tohold and output the peak in the period. In addition, the timinggenerator 25 c performs timing control such that the A/D converter 25 b2 converts the held and output peak to a digital value.

[0308] The timing generator 25 c further sends a signal shown in FIG.19(f), indicating a sampling period corresponding to a period of thethird pulse P#3 in the RF signal to the peak holding circuit 25 a3 tohold and output the peak in the period. In addition, the timinggenerator 25 c performs timing control such that the A/D converter 25 b3converts the held and output peak to a digital value.

[0309] Although not shown in the figure, the timing generator 25 cgenerates signals indicating sampling periods for the fourth pulse P#4to the n-th pulse P#n and signals for controlling A/D conversion timing.

[0310] Furthermore, the timing generator 25 c sends a signal shown inFIG. 19(g), which indicates a sampling period corresponding to a spaceperiod in the RF signal to the sample-and-hold circuit 25 d at a pointof time, such as when a laser-power compensation operation is started,to hold and output the peak in the period. The timing generator 25 calso applies timing control to the A/D converter 25 e so as to convertthe held and output peak to a digital value.

[0311] With this, the A/D converter 25 e outputs the quantity LSP ofreflected light as the digital value, and a sampled-value input section10 a in a system controller 10 reads the quantity LSP of reflected lightas information used for calculating compensated peak PK1′ (value A′).

[0312] The A/D converter 25 b1 outputs the peak PK1 as the digitalvalue, and the sampled-value input section 10 a in the system controller10 reads the peak PK1 as information used for adjusting the calculatedcompensated peak PK1′ (value A′).

[0313] The A/D converters 25 b 2 to 25 b(n) also input the peaks PK2, .. . , and PKn of the subsequent pulses to the sampled-value inputsection 10 a. The sampled-value input section 10 a obtains the averageavPK thereof by the calculation of (PK2+PK3+. . . +PKn)/n, and sets thecalculated average avPK in the value B.

[0314] Then, an estimation calculation section 10 b needs to obtain theratio B/A′ from the values A′ and B, and a compensation calculationsection 10 c needs to generate a laser-power compensation signal in thesame way as described above. In other words, the processing shown inFIG. 13, FIG. 14, or FIG. 17 needs to be performed.

[0315]FIG. 20 shows a case in which the bottom values BT2 and BT3 of thesecond pulse P#2 and the third pulse P#3 are used as the value B. Afigure showing the structure of a pulse sampling section 25 is omitted.In this case, a bottom holding circuit for the second pulse P#2 and abottom holding circuit for the third pulse P#3 in addition to asample-and-hold circuit 25 d for the quantity LSP of reflected light ata space period (and a peak holding circuit 25 a 1 for the first pulseP#1 if a process for adjusting A′ is performed), and A/D converterscorresponding thereto need to be provided.

[0316] A timing generator 25 c outputs signals which specify samplingperiods as shown in FIG. 20(d), FIG. 20(e), FIG. 20(f), and FIG. 20(g)to sample the peak PK1, the bottom values BT2 and BT3, and the quantityLSP of reflected light at predetermined points of time.

[0317] With this, a sampled-value input section 10 a in a systemcontroller 10 receives the peak PK1, the bottom values BT2 and BT3, andthe quantity LSP of reflected light. The sampled-value input section 10a reads the peak PK1 and the quantity LSP of reflected light forcalculating and adjusting the value A′, and also reads the bottom valuesBT2 and BT3 as the value B. Either the bottom value BT2 or the bottomvalue BT3 may be used as the value B. Alternatively, the average(BT2+BT3)/2 may be used as the value B.

[0318]FIG. 21 shows a case in which the center values of the secondpulse P#2 and subsequent pulses are used as the value B. A figureshowing the structure of a pulse sampling section 25 is omitted. In thiscase, peak holding circuits for the second pulse and subsequent pulsesP#2 to P#n, bottom holding circuits for the second pulse and subsequentpulses P#2 to P#n in addition to a sample-and-hold circuit 25 d for thequantity LSP of reflected light at a space period (and a peak holdingcircuit 25 a 1 for the first pulse P#1 if a process for adjusting A′ isperformed), and A/D converters corresponding thereto need to beprovided.

[0319] A timing generator 25 c outputs signals which specify samplingperiods as shown in FIG. 21(d), FIG. 21(e), FIG. 21(f), and FIG. 21(g)to sample the peak PK1, the peak values and bottom values of the periodsof the second pulse and subsequent pulses P#2 to P#n, and the quantityLSP of reflected light at predetermined points of time.

[0320] With this, a sampled-value input section 10 a in a systemcontroller 10 receives the peak PK1, the peak and bottom values of thesecond pulse P#2 and subsequent pulses, and the quantity LSP ofreflected light. The sampled-value input section 10 a reads the peak PK1and the quantity LSP of reflected light for calculating and adjustingthe value A′. The sampled-value input section 10 a also calculatescenter values CT(2−n) by dividing the sums of the peak and bottom valuesof the second pulse P#2 and subsequent pulses by 2 and uses them as thevalue B.

[0321]FIG. 22 shows a case in which the average av of all sampled valuesof the second and subsequent pulses P#2 to P# is used as the value B. Afigure showing the structure of a pulse sampling section 25 is omitted.In this case, sampling circuits for the second and subsequent pulses P#2to P#n in addition to a sample-and-hold circuit 25 d for the quantityLSP of reflected light at a space period (and a peak holding circuit 25a 1 for the first pulse P#1 if a process for adjusting A′ is performed),and A/D converters corresponding thereto need to be provided.

[0322] A timing generator 25 c outputs signals which specify samplingperiods as shown in FIG. 22(d), FIG. 22(e), and FIG. 22(f) to sampleamplitudes at intervals of predetermined sampling periods in the zone ofthe second pulse P#2 to the n-th pulse, and the quantity LSP ofreflected light at predetermined points of time.

[0323] With this, a sampled-value input section 10 a in a systemcontroller 10 receives the peak PK1, the sampled values of the secondpulse P#2 and subsequent pulses, and the quantity LSP of reflectedlight. The sampled-value input section 10 a reads the peak PK1 and thequantity LSP of reflected light for calculating and adjusting the valueA′. The sampled-value input section 10 a also calculates the average avby dividing the sum of the sampled values of the second pulse P#2 andsubsequent pulses by the number of samples and uses it as the value B.

[0324]FIG. 23 shows a case in which the bottom values of the second andsubsequent pulses P#2 to P# are used as the value B. A figure showingthe structure of a pulse sampling section 25 is omitted. In this case,bottom holding circuits for the second and subsequent pulses P#2 to P#nin addition to a sample-and-hold circuit 25 d for the quantity LSP ofreflected light at a space period (and a peak holding circuit 25 a 1 forthe first pulse P#1 if a process for adjusting A′ is performed), and A/Dconverters corresponding thereto need to be provided.

[0325] A timing generator 25 c outputs signals which specify samplingperiods as shown in FIG. 23(d), FIG. 23(e), and FIG. 23(f) to sample thepeak PK1, bottom values in the zone of the second pulse P#2 to the n-thpulse, and the quantity LSP of reflected light at predetermined pointsof time.

[0326] With this, a sampled-value input section 10 a in a systemcontroller 10 receives the peak PK1, the bottom values of the secondpulse P#2 and subsequent pulses, and the quantity LSP of reflectedlight. The sampled-value input section 10 a reads the peak PK1 and thequantity LSP of reflected light for calculating and adjusting the valueA′, and uses the bottom values of the second pulse P#2 and subsequentpulses as the value B.

[0327] As described above, various items can be used as the values A′and B used for obtaining the ratio B/A′. The compensated values of thecenter value CT1 or the modulation value (PK1−BT1) of the first pulseP#1, that is, a center value CT1′ or a modulation value (PK1−BT1)′, maybe used as the value A1.

[0328] Further various items may be used as the value B, such as thepeaks, the bottom values, the center values, the average, or themodulation values (peak−bottom value) corresponding to the second pulseP#2 and subsequent pulses.

[0329] The reference ratio (B/A′)ref stored in the memory 27 in advanceas table data needs to correspond to the values A′ and B. When thecompensated center value CT1′ of the center value CT1 of the first pulseP#1 is used as the value A′ and the center value CT2 of the second pulseP#2 is used as the value B, for example, a reference ratio (B/A′)refneeds to be the most appropriate CT2/CT1′ value.

[0330] In the embodiment, the disk drive apparatus is the recording andreproduction apparatus which handles DVD-Rs. The disk drive apparatuscan also be a recording apparatus which handles other types of recordingmedia.

[0331] From the point of view of the operational principle of thepresent invention, the present invention can be preferably applied todisk drive apparatuses which handle recording media having an organicpigment film, which has a quick mark-generation response to laserillumination. The present invention can also be preferably applied torecording apparatuses which handle not recording media having an organicpigment film but recording media having a quick mark-generation responseto laser illumination, that is, recording media in which reflected lightincludes an effect of generated marks.

[0332] The disk drive apparatus 30 shown in FIG. 10 is connected to thehost computer 80. An optical recording apparatus according to thepresent invention can be an apparatus not connected to the host computer80 or others. In this case, an operation section and a display sectionare provided and a data input-and-output interface section has adifferent structure from that shown in FIG. 10. In other words,recording and reproduction needs to be performed according to user'soperations, and a terminal section for inputting and outputting variousdata needs to be formed.

[0333] As understood from the above description, according to thepresent invention, when data is recorded (a data string is generated bymarks and spaces) in an organic-pigment recording medium bypulse-train-manner laser outputs, for example, a space-period signalvalue corresponding to a space period is detected in a reflected-lightinformation signal to estimate a first-pulse signal value correspondingto a first pulse in the pulse-train-manner laser outputs. Asecond-and-subsequent-pulse signal value corresponding to second andsubsequent pulses in the pulse-train-manner laser outputs is alsodetected in the reflected-light information signal. The ratio betweenthe estimated first-pulse signal and the detectedsecond-and-subsequent-pulse signal value is obtained, and a laser-powercompensation signal is generated by using the obtained ratio and areference ratio to control laser output power. This means that arecording state itself, that is, pit mark generation, is observed tocompensate laser power. The laser power is compensated to be mostappropriate with all environmental conditions (all factors that affectmark generation) at the point of recording being taken into account.More specifically, the laser power is controlled for a change in theenergy absorption efficiency of the recording medium caused bywavelength fluctuation due to the temperature dependency of the I-Lcharacteristic of the semiconductor laser or aging, and film unevennesson a surface of the recording medium.

[0334] Therefore, the most appropriate mark-generation operation isalways implemented, and the quality (jitter and others) of an RF signalis improved when reproduction.

[0335] When the first-pulse signal value corresponding to the firstpulse of the pulse-train-manner laser outputs is detected in thereflected-light information, and the first-pulse signal value estimatedby using the space-period signal is corrected by using the first-pulsesignal value detected by the signal detection means, the estimatedfirstpulse signal is changed to the most appropriate value generatedwith reflectivity unevenness on the recording medium being taken intoaccount. With this, more appropriate laser power control is implemented.

[0336] It is preferred in the above-described laser-power compensationprocessing that the peak, the center value, or the modulation value ofthe reflected-light information signal, corresponding to the first pulsein the pulse-train-manner laser outputs be used as the first-pulsesignal value, and the peak, the center value, the bottom value, theaverage, or the modulation value of the reflected-light informationsignal, corresponding to the whole or part of the second and subsequentpulses in the pulse-train-manner laser outputs be used as thesecond-and-subsequent-pulse signal value.

[0337] When the most appropriate ratio between the first-pulse signalvalue and the second-and-subsequent-pulse signal value is stored inadvance according to each of various conditions related to a recordingoperation, and a ratio suited to the current condition is selected amongthe stored ratios and used as the reference ratio, various recordingconditions, such as a medium type, a linear velocity, and target laserpower, can be appropriately handled.

1. An optical recording apparatus for recording data in a recordingmedium, characterized by comprising: recording processing means forapplying encoding processing to data to be recorded to generate encodeddata and for generating laser driving pulses used for executingpulse-train-manner laser outputs, according to the encoded data;recording-head means for emitting the laser outputs to the recordingmedium according to the laser driving pulses to execute recording of adata string formed of a mark and a space on the recording medium;reflected-light information signal detection means for detecting areflected-light information signal obtained when the recording-headmeans emits the laser outputs; signal-value detection means fordetecting a space-period signal value corresponding to a period of thespace and a second-and-subsequent-pulse signal value corresponding tosecond and subsequent pulses in the pulse-train-manner laser outputs, inthe reflected-light information signal detected by the reflected-lightinformation signal detection means; estimation means for estimating afirst-pulse signal value corresponding to a first pulse in thepulse-train-manner laser outputs by using the space-period signal valuedetected by the signal-value detection means; calculation means forobtaining the ratio between the second-and-subsequent-pulse signal valuedetected by the signal-value detection means and the first-pulse signalvalue obtained by the estimation means and for generating a laser-powercompensation signal by using the obtained ratio and a reference ratio;and laser-power control means for controlling the power of the laseroutputs according to the laser-power compensation signal sent from thecalculation means.
 2. An optical recording apparatus according to claim1, characterized in that the recording medium has an organic pigmentfilm as a recording layer.
 3. An optical recording apparatus accordingto claim 1, characterized in that the signal-value detection meansfurther detects the first-pulse signal value corresponding to the firstpulse in the pulse-train-manner laser outputs, and the estimation meanscorrects the first-pulse signal value estimated by using thespace-period signal value, by using the first-pulse signal valuedetected by the signal-value detection means.
 4. An optical recordingapparatus according to claim 1, characterized in that the first-pulsesignal value is the peak, the center value, or the modulation value ofthe reflected-light information signal, corresponding to the first pulsein the pulse-train-manner laser outputs.
 5. An optical recordingapparatus according to claim 1, characterized in that thesecond-and-subsequent-pulse signal value is the peak, the center value,the bottom value, the average, or the modulation value of thereflected-light information signal, corresponding to the whole or partof the second and subsequent pulses in the pulse-train-manner laseroutputs.
 6. An optical recording apparatus according to claim 1,characterized in that the calculation means stores in advance the mostappropriate ratio between the first-pulse signal value and thesecond-and-subsequent-pulse signal value according to each of variousconditions related to a recording operation, and selects a ratio suitedto the current condition among the stored ratios to use it as thereference ratio.
 7. A laser-power control method for an opticalrecording apparatus which applies pulse-train-manner laser outputs to arecording medium having an organic pigment film to record a data stringformed of a mark and a space on the recording medium, characterized bycomprising the steps of: detecting a space-period signal valuecorresponding to a period of the space and a second-and-subsequent-pulsesignal value corresponding to second and subsequent pulses in thepulse-train-manner laser outputs, in a reflected-light informationsignal obtained during the laser outputs; estimating a first-pulsesignal value corresponding to a first pulse in the pulse-train-mannerlaser outputs by using the detected space-period signal value; obtainingthe ratio between the detected second-and-subsequent-pulse signal valueand the estimated first-pulse signal value, and generating a laser-powercompensation signal by using the obtained ratio and a reference ratio;and controlling the power of the laser outputs according to thelaser-power compensation signal.
 8. A laser-power control methodaccording to claim 7, characterized in that the first-pulse signal valuecorresponding to the first pulse in the pulse-train-manner laser outputsis detected in the reflected-light information signal obtained duringthe laser outputs, and the first-pulse signal value estimated by usingthe space-period signal value is corrected by using the detectedfirst-pulse signal value.
 9. A laser-power control method according toclaim 7, characterized in that the first-pulse signal value is the peak,the center value, or the modulation value of the reflected-lightinformation signal, corresponding to the first pulse in thepulse-train-manner laser outputs.
 10. A laser-power control methodaccording to claim 7, characterized in that thesecond-and-subsequent-pulse signal value is the peak, the center value,the bottom value, the average, or the modulation value of thereflected-light information signal, corresponding to the whole or partof the second and subsequent pulses in the pulse-train-manner laseroutputs.
 11. A laser-power control method according to claim 7,characterized in that the most appropriate ratio between the first-pulsesignal value and the second-and-subsequent-pulse signal value is storedin advance according to each of various conditions related to arecording operation, and a ratio suited to the current condition isselected among the stored ratios and used as the reference ratio.
 12. Anoptical recording apparatus for recording data in a recording medium,characterized by comprising: a laser driving driver for generating laserdriving pulses used for executing pulse-train-manner laser outputs,according to data to be recorded; a recording head for emitting thelaser outputs to the recording medium according to the laser drivingpulses to execute recording of a data string formed of a mark and aspace on the recording medium; a reflected-light information signaldetector for detecting a reflected-light information signal obtainedfrom the recording medium when the recording head emits the laseroutputs; a signal-value detection circuit for detecting a space-periodsignal value corresponding to a period of the space and asecond-and-subsequent-pulse signal value corresponding to second andsubsequent pulses in the pulse-train-manner laser outputs, in thereflected-light information signal detected by the reflected-lightinformation signal detector; an estimation circuit for estimating afirst-pulse signal value corresponding to a first pulse in thepulse-train-manner laser outputs by using the space-period signal valuedetected by the signal-value detection circuit; a calculation circuitfor applying a calculation to the second-and-subsequent-pulse signalvalue detected by the signal-value detection circuit and the first-pulsesignal value obtained by the estimation circuit and for generating alaser-power compensation signal by using an obtained value and areference value; and a laser-power controller for controlling the powerof the laser outputs according to the laser-power compensation signalsent from the calculation circuit.
 13. An optical recording apparatusaccording to claim 12, characterized in that the recording medium has anorganic pigment film as a recording layer.
 14. An optical recordingapparatus according to claim 12, characterized in that the signal-valuedetection circuit further detects the first-pulse signal valuecorresponding to the first pulse in the pulse-train-manner laseroutputs, and the estimation circuit corrects the first-pulse signalvalue estimated by using the space-period signal value, by using thefirst-pulse signal value detected by the signal-value detection circuit.15. An optical recording apparatus according to claim 12, characterizedin that the first-pulse signal value is the peak, the center value, orthe modulation value of the reflected-light information signal,corresponding to the first pulse in the pulse-train-manner laseroutputs.
 16. An optical recording apparatus according to claim 12,characterized in that the second-and-subsequent-pulse signal value isthe peak, the center value, the bottom value, the average, or themodulation value of the reflected-light information signal,corresponding to the whole or part of the second and subsequent pulsesin the pulse-train-manner laser outputs.
 17. An optical recordingapparatus according to claim 12, characterized in that the calculationcircuit stores in advance the most appropriate ratio between thefirst-pulse signal value and the second-and-subsequent-pulse signalvalue according to each of various conditions related to a recordingoperation, and selects a ratio suited to the current condition among thestored ratios to use it as the reference ratio.